B7200 hydraulic steering

[Paul Allwood]

You already have a PS unit. This pump or similar, a shaft coupler, and some plumbing will power it.

Dan

0.55 cu in Dynamic GPF1091PA Hydraulic Pump [902167]

surpluscenter.com

G'day Dan - the best price I've found for a similar pump from an Australian supplier is at the following eBay link....

Hydraulic Group 2 Gear Pumps, SAE A, 5/8" Keyed Shaft | eBay Australia

5/8" Keyed Shaft. - SAE A 2 Bolt Mount.

ebay.us

It includes options of 6 and 12 cc/rev. The one you suggested above is about 9 cc/rev.

Does all of the excess flow that's delivered to the orbitrol valve and not used for steering go back to the tank ?

Can I do any harm by having too much excess flow ?

Am I better to choose a higher or lower displacement pump if I can't match the one you suggested ?

Would you suggest tapping into existing lines to use the existing tank and hydraulic fluid, better to fit a separate tank/filter, or doesn't really matter ?

Thanks

 

[TheOldHokie]

G'day Dan - the best price I've found for a similar pump from an Australian supplier is at the following eBay link....

Hydraulic Group 2 Gear Pumps, SAE A, 5/8" Keyed Shaft | eBay Australia

5/8" Keyed Shaft. - SAE A 2 Bolt Mount.

ebay.us

It includes options of 6 and 12 cc/rev. The one you suggested above is about 9 cc/rev.

Does all of the excess flow that's delivered to the orbitrol valve and not used for steering go back to the tank ?

Can I do any harm by having too much excess flow ?

Am I better to choose a higher or lower displacement pump if I can't match the one you suggested ?

Would you suggest tapping into existing lines to use the existing tank and hydraulic fluid, better to fit a separate tank/filter, or doesn't really matter ?

Thanks

ALL of the flow goes through the PS valve and then back to tank.

The valve will have a flow rating but I have no idea what yours is. Flow ratings are based on pressure drop across ths valve and desugners typically aim for just a few PSI. That does not mean the valve cant handle a higher flow. Higher flow simply increases the pressure drop which wastes energy (HP) in the form of heat. So a little higher is fine but 10X would be a bad choice. I would suggest you lookup the PS flow specification for the donor tractor and use that as your target.

The pump I linked is a SAE AA form factor and yours is SAE A which is physically much larger. I suggest you look for an SAE AA pump - much easier to fit inti the soace you have avaikable and they will be smaller displacement as well. You should have no problem finding them.

I think Concentric is a prominant brand in Europe. There are a couple others but the names escape me at the moment. I dont know what AU import duties are like but I have no problem shipping a pump to AU.

Dan

 

[Paul Allwood]

ALL of the flow goes through the PS valve and then back to tank.

The valve will have a flow rating but I have no idea what yours is. Flow ratings are based on pressure drop across ths valve and desugners typically aim for just a few PSI. That does not mean the valve cant handle a higher flow. Higher flow simply increases the pressure drop which wastes energy (HP) in the form of heat. So a little higher is fine but 10X would be a bad choice. I would suggest you lookup the PS flow specification for the donor tractor and use that as your target.

The pump I linked is a SAE AA form factor and yours is SAE A which is physically much larger. I suggest you look for an SAE AA pump - much easier to fit inti the soace you have avaikable and they will be smaller displacement as well. You should have no problem finding them.

I think Concentric is a prominant brand in Europe. There are a couple others but the names escape me at the moment. I dont know what AU import duties are like but I have no problem shipping a pump to AU.

Dan

Haha - I didn't notice the "A" - thanks. I'll keep looking and see if I can find out the donor tractor model.

 

[Paul Allwood]

ALL of the flow goes through the PS valve and then back to tank.

The valve will have a flow rating but I have no idea what yours is. Flow ratings are based on pressure drop across ths valve and desugners typically aim for just a few PSI. That does not mean the valve cant handle a higher flow. Higher flow simply increases the pressure drop which wastes energy (HP) in the form of heat. So a little higher is fine but 10X would be a bad choice. I would suggest you lookup the PS flow specification for the donor tractor and use that as your target.

The pump I linked is a SAE AA form factor and yours is SAE A which is physically much larger. I suggest you look for an SAE AA pump - much easier to fit inti the soace you have avaikable and they will be smaller displacement as well. You should have no problem finding them.

I think Concentric is a prominant brand in Europe. There are a couple others but the names escape me at the moment. I dont know what AU import duties are like but I have no problem shipping a pump to AU.

Dan

The hydraulic steering components are from a BS2230. I found the following specs:

The power steering flow rates in metric and imperial units in this table don't match - 15.4 L/min doesn't equal 1.4 gals/min, so there's a typo somewhere....
- 15.4 l/min = 4.1 GPM (so is the 1.4 typed backwards ?), or
- 1.4 GPM = 5.4 l/min (so has a 1 been added by mistake ?).

Which do you think is the correct steering flow rate - 1.4 or 4.1 GPM (5.4 or 15.4 l/min) ?

Not sure if it helps but I found specs on the BX2230 steering valve that stated 50 cc/rev. I haven't been able to find specs for the steering cylinder.

 

[Russell King]

Good attempt at resolving the error but you really got messed around by both being typographical errors that “were close” in both cases.

I would ASSUME that the l/minute is correct since Japan is ”fully SI”.

But good luck in your quest. @TheOldHokie may have the information handy???

 

[TheOldHokie]

The hydraulic steering components are from a BS2230. I found the following specs:

View attachment 170120

The power steering flow rates in metric and imperial units in this table don't match - 15.4 L/min doesn't equal 1.4 gals/min, so there's a typo somewhere....
- 15.4 l/min = 4.1 GPM (so is the 1.4 typed backwards ?), or
- 1.4 GPM = 5.4 l/min (so has a 1 been added by mistake ?).

Which do you think is the correct steering flow rate - 1.4 or 4.1 GPM (5.4 or 15.4 l/min) ?

Not sure if it helps but I found specs on the BX2230 steering valve that stated 50 cc/rev. I haven't been able to find specs for the steering cylinder.

Good catch. A quick review of some other BX models indicates priority flow of ~2 GPM. That sounds more lijely than 4 GPM which is the implement side. Too bad you cant measure pressure drop before buying a pump. Hint, hint

Dan

 

[Paul Allwood]

Good catch. A quick review of some other BX models indicates priority flow of ~2 GPM. That sounds more lijely than 4 GPM which is the implement side. Too bad you cant measure pressure drop before buying a pump. Hint, hint

Dan

Using 2 GPM as a target

If I aim for around 2 GPM (7.6 l/min) at 2000 rpm I would need a pump with a displacement of 3.8 ml/rev (0.23 cu in/rev). This is about half the displacement of your original suggested pump above - what have I messed up ?

Pressure drop

I'm not sure how good I am at picking up hints - are you suggesting I attempt to set up something to measure the pressure drop through the steering valve ?

So now I'm thinking as I'm typing, sort of like thinking out loud, so be gentle....I guess I would want this with no steering input ? For flowrate I could time the oil into a bucket which could get a bit messy, or connect into the PB line out of the loader valve and assume I'm getting the rated flowrate....??? Am I then looking for a flowrate that doesn't give excessive (whatever that is) pressure drop but it's sufficient to operate the steering ?

Steering control valve

I found a spec on the steering control valve that stated a displacement of 50 ml/rev. I don't have the cylinder specs, but assuming 4 turns lock to lock in 2 seconds, I would need a minimum flowrate of 200 ml/2 s = 6 l/min.

At 2000 rpm this would require a pump displacement of 3 ml/rev. Is it just luck that this came out close to the 3.8 ml/rev figure I came up with above ?

 

[TheOldHokie]

Using 2 GPM as a target

If I aim for around 2 GPM (7.6 l/min) at 2000 rpm I would need a pump with a displacement of 3.8 ml/rev (0.23 cu in/rev). This is about half the displacement of your original suggested pump above - what have I messed up ?

Pressure drop

I'm not sure how good I am at picking up hints - are you suggesting I attempt to set up something to measure the pressure drop through the steering valve ?

So now I'm thinking as I'm typing, sort of like thinking out loud, so be gentle....I guess I would want this with no steering input ? For flowrate I could time the oil into a bucket which could get a bit messy, or connect into the PB line out of the loader valve and assume I'm getting the rated flowrate....??? Am I then looking for a flowrate that doesn't give excessive (whatever that is) pressure drop but it's sufficient to operate the steering ?

Steering control valve

I found a spec on the steering control valve that stated a displacement of 50 ml/rev. I don't have the cylinder specs, but assuming 4 turns lock to lock in 2 seconds, I would need a minimum flowrate of 200 ml/2 s = 6 l/min.

At 2000 rpm this would require a pump displacement of 3 ml/rev. Is it just luck that this came out close to the 3.8 ml/rev figure I came up with above ?

I think you are making things a little more complicafed than needed.

My initial 4 GPM was a pure guess.

A 2 GPM pump drops off to <1 GPM at low RPM. Thats pretty skimpy for any PS system. Thats one of the benefits of a priority valve design. It keeps the PS flow more or less constant across engine RPM.

You should be looking at the max flow the PS controller can handle in neutral

Pressure drop is measured by putting a gauge on the inlet and outlet sides of the valve and subtracting the two readings as you vary RPMs ( e.g. pump flow). You have a 4 GPM source already on the tractor. It should be easy to temporarily hook the PS controller into the loader PB circuit and get some hard data as a sanity check. Takes two "low pressure" gauges, two tees, and a couple hoses. Speaking of pressure, does the controller have a built in relief?

Dan

 

[Paul Allwood]

I think you are making things a little more complicafed than needed.

My initial 4 GPM was a pure guess.

A 2 GPM pump drops off to <1 GPM at low RPM. Thats pretty skimpy for any PS system. Thats one of the benefits of a priority valve design. It keeps the PS flow more or less constant across engine RPM.

You should be looking at the max flow the PS controller can handle in neutral

Pressure drop is measured by putting a gauge on the inlet and outlet sides of the valve and subtracting the two readings as you vary RPMs ( e.g. pump flow). You have a 4 GPM source already on the tractor. It should be easy to temporarily hook the PS controller into the loader PB circuit and get some hard data as a sanity check. Takes two "low pressure" gauges, two tees, and a couple hoses. Speaking of pressure, does the controller have a built in relief?

Dan

I can't find much info on the steering valve, but found this from a Google search that states that the steering valve had an internal relief valve....

The "max flow the PS controller can handle in neutral" - is there a maximum pressure drop that goes with determining the maximum flowrate, otherwise what determines the maximum flowrate ?

 

[TheOldHokie]

I can't find much info on the steering valve, but found this from a Google search that states that the steering valve had an internal relief valve....

View attachment 170140

The "max flow the PS controller can handle in neutral" - is there a maximum pressure drop that goes with determining the maximum flowrate, otherwise what determines the maximum flowrate ?

I dont want this to fester into a "paralysis by over analyisis" discussion as happens all to often here. You just need a pump big enough to provide enough flow at idle but not so large it generates excessive heat at 2200 RPM.

That said max flow specifications are subjective numbers. One OEM might use 20 PSI drop and another might use 50. In real life the system designer has to make the final determination based on the overall system configuration. In an open center system ten valves ganged together is a far different situation than one.

In this case I doubt 2 vs 4 GPM is going to be significant in terms of pressure drop in your little one valve circuit. But absent a reliable specification what I would like to see is a pressure drop curve for the valve to sanity check that WAG. Here is an example. These valves are used in applications as high as 20 GPM but more commonly 8-12 GPM. Curve number 2 is the P->T situation we are discussing. If you want to go to the trouble you can measure your actual pressure drop up to 4 GPM using your tractor as a test rig. Its not a lot of extra trouble and what I would do because I hate guessing but I am not you.

 

[Paul Allwood]

I dont want this to fester into a "paralysis by over analyisis" discussion as happens all to often here. You just need a pump big enough to provide enough flow at idle but not so large it generates excessive heat at 2200 RPM.

That said max flow specifications are subjective numbers. One OEM might use 20 PSI drop and another might use 50. In real life the system designer has to make the final determination based on the overall system configuration. In an open center system ten valves ganged together is a far different situation than one.

In this case I doubt 2 vs 4 GPM is going to be significant in terms of pressure drop in your little one valve circuit. But absent a reliable specification what I would like to see is a pressure drop curve for the valve to sanity check that WAG. Here is an example. These valves are used in applications as high as 20 GPM but more commonly 8-12 GPM. Curve number 2 is the P->T situation we are discussing. If you want to go to the trouble you can measure your actual pressure drop up to 4 GPM using your tractor as a test rig. Its not a lot of extra trouble and what I would do because I hate guessing but I am not you.

View attachment 170142

Haha - I'm pretty good at paralysis by analysis so also happy to try and avoid it.

I found a Sauer Danfoss part number along with the Kubota part number on a US parts supplier site, and from that found the tech manual covering the steering valve. This included the pressure drop vs flowrate graph below:

The applicable model is the OSPM 50 ON so it's curve 'B'. Approximately 25 psi pressure drop at 8 l/min, and 50 psi at 12 l/min.

To work out what is enough flow (I'm making this up, but it seems to make sense):
- Steering valve 50 ml/rev
- Assume 4 turns/2 seconds lock to lock
- 200 ml/2 seconds = 6 l/min

If I need this flow at idle of 1000 rpm that gives me a pump displacement of 6 ml/rev.

If I have 6 l/min at 1000 rpm, I'll have about 15 l/m at 2500 rpm which gives me a pressure drop off about 75 psi across the steering valve.

This is based on my guess at how to work out the minimum flow requirement from steering valve displacement, lock to lock turns and time.

 

[Paul Allwood]

Is there anyone out there with a BX2230 or BX2200 who can tell me how many turns of the steering wheel are required from lock to lock ?

Many thanks.

 

[TheOldHokie]

Is there anyone out there with a BX2230 or BX2200 who can tell me how many turns of the steering wheel are required from lock to lock ?

Many thanks.

Forget lock to lock. At 3 GPM the pressure drop P->T is less than 50 PSI. Plenty of flow and well within the requirements of the cylinder.

Dan

 

[Paul Allwood]

Forget lock to lock. At 3 GPM the pressure drop P->T is less than 50 PSI. Plenty of flow and well within the requirements of the cylinder.

Dan

3 GPM at 2500 rpm - 0.28 cu in per rev ? SAE AA.

 

[TheOldHokie]

3 GPM at 2500 rpm - 0.28 cu in per rev ? SAE AA.

Should work but I would still bench test the unit using the loader before buying.

 

[TheOldHokie]

When I say bench test that would include operating the controller at both low and high engine RPM to evaluate steering cylinder response.

Dan